The present invention relates generally to duct assemblies for transporting pressurized fluid such as heating and cooling air, and more particularly to a duct assembly having robust corner connections and a method of making such a duct assembly.
Duct assemblies used to transport pressurized fluid in buildings (e.g., for forced air HVAC systems) are conventionally formed in sections and secured together to form longer spans as needed. A duct section is typically formed of sheet metal into a rectangular shape having four sides and bent or seamed corners at the intersections of the sides. A flange extends essentially perpendicularly outward from each side at both ends of the duct section. The sections are positioned end-to-end so the flanges of one section align with the flanges of the adjacent section and the aligned flanges are fastened together to form the duct assemblies. The flanges which are formed as part of each duct section are not continuous. Rather, there are gaps at each place on the duct sections where adjacent flanges meet for manufacturing convenience. Stamped corner pieces are inserted in channels formed in each flange so they span the gap at each place on the duct section where adjacent flanges meet. When the duct sections are positioned end-to-end, the stamped corner pieces of one duct section are aligned with stamped corner pieces of the adjacent duct section. Fasteners are inserted through holes extending through the stamped corner pieces to clamp the duct sections together. Frequently, gaskets are placed between aligned flanges to achieve an airtight seal and clips are used to hold the aligned flanges together between the stamped corner pieces.
Stamped corner pieces are sometimes inserted in the duct section at one location and transported to another location for attachment to other duct sections to form duct assemblies. The corner pieces are snapped into the flanges, which are formed with return bends at their free ends to bear against the corner piece with a spring force to hold the corner pieces in the flange. It is also known to press in the corner pieces and crimp over the return bends of the flanges to secure them. However in many cases, the snap connection of the corner piece into the flange is not completely secure, even when crimping is used. Not only does this allow the corner pieces to become separated from the flanges more easily, but it also allows adjacent flanges of the duct assembly to move independently of each other. When the corner pieces become separated from the flanges, additional time is required to reinsert the corner pieces in the flanges. Moreover, if the corner pieces become separated when the duct sections are overhead, the corner pieces can fall on workers below. Still further, if the corner pieces move independently from the flanges, adjacent flanges of the duct assembly can move independently from each other permitting the duct sections to move with respect to each other thereby allowing fluid to leak from between the joints. Several connection systems are commercially available. Many of these require unique components (e.g., special corner pieces) or special equipment to connect the duct sections. In many applications, a separate gasket must be secured between the sections for sufficient sealing, which complicates assembly and increases the chances for faulty assembly. Finally, the insertion of the corner pieces into the flanges provides no rigid interconnection of adjacent flanges and therefore minimal angular rigidity to the joint between the duct sections or to the duct assembly.
Among the several objects and features of the present invention may be noted the provision of a duct assembly which has improved strength at its joint; the provision of such a duct assembly which maintains a tight seal at the joint; the provision of such a duct assembly which has fewer parts constituting the joint; the provision of such a duct assembly which does not require a gasket; the provision of such a duct assembly which can use modified conventional corner pieces to form the joint connection; the provision of a corner flange connection member for use in the duct assembly which does not require connection to the duct section prior to assembly of the joint; the provision of a method for quickly and inexpensively interconnecting duct sections; the provision of such a method of assembly which does not require insertion of a corner flange connection member or corner piece to a duct section prior to final assembly of the joint; the provision of such a method of assembly which permits the duct sections to be shipped to the site in a compact, broken down configuration; and the provision of such a method of assembly which can be carried out at the building site with equipment on hand.
Briefly, a duct assembly of the present invention for transporting pressurized fluid therethrough comprises duct sections, each having sides extending between opposite ends. Each of the sides joins an adjacent side and has an integral flange extending laterally outward from each end. The integral flanges and sides are formed as one piece from sheet metal material. The duct sections are disposed in end-to-end relation with the integral flanges of one duct section generally in registration with the integral flanges of the other duct section to define a joint. Fasteners pass through the aligned flanges for attaching the duct sections in generally sealing relation at the joint.
In another aspect of the present invention, a corner flange connection member is capable of attachment to a duct section having sides extending between opposite ends. Each of the sides joins an adjacent side and has an integral flange extending laterally outward from each end. The integral flange on each side is adjacent to the integral flange of the adjacent side at each end of the duct section. The corner flange connection member comprises a first leg and a second leg extending generally at angles relative to each other so that when the corner flange connection member is installed at adjacent flanges at an end of the duct section, a first leg overlies a first of the adjacent integral flanges and a second leg overlies a second of the adjacent integral flanges. The first leg has a first hole therein located on the first leg for overlying the first integral flange and the second leg has a first hole therein located on the second leg for overlying the second integral flange. The first holes are adapted to receive fasteners therethrough for joining the integral flanges of the duct section to integral flanges of another duct section.
In still another aspect of the present invention, a method of assembling two duct sections in end-to-end relation is disclosed. Each duct section has sides extending between opposite ends of the duct section and joins an adjacent side of the duct section. The duct section side has an integral flange extending laterally outward from each end. The integral flanges and sides are formed as one piece from sheet metal material. Each integral flange is adjacent to another of the integral flanges where sides meet at each end of the duct section. The method comprises the steps of arranging the duct sections in generally end-to-end relation with each other such that the integral flanges of one duct section are generally aligned with integral flanges of the other duct section, inserting fasteners through corresponding holes in both of the aligned integral flanges, and tightening the fasteners to secure the duct sections together.
Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.